The disclosure relates generally to hydrous clay containing green monoliths and more specifically to hydrous clay containing green monoliths that can exhibit reduced shrinkage during firing.
In the formation of ceramic bodies, e.g., silicon carbide, cordierite, mullite, alumina, or aluminum titanate bodies, green monoliths are typically fired at high temperatures for an extended period of time. During firing, the green bodies often experience one or more shrinkage events. For example, during the firing of hydrous clay containing green monoliths, the bodies often shrink during a time (and temperature) in the firing cycle that corresponds to a clay dehydroxylation event. Such shrinking can lead to the formation of cracks and other undesirable defects in the resulting ceramic articles.
Various methods have been employed to control the shrinkage of such hydrous clay containing green monoliths. One method, such as that described in U.S. Pat. No. 4,001,028, involves simply reducing the amount of hydrous clay in the batch composition. However, reducing the amount of hydrous clay can lead to certain potential disadvantages, such as creating a less plastic batch material—that is more difficult to extrude and/or undesirable changes with respect to the properties of the fired ceramic body.
Other methods have involved characterizing the clay morphology using an analytical technique, correlating such characterization with a desired characteristic, and then selecting clay that will help enable the resulting composition to exhibit the desired characteristic. For example, U.S. Pat. No. 7,481,962, discloses an analytical technique for determining a clay “cleavage index” and then setting a limit on that index for clay used in a composite batch composition.